The surveyors elevation measuring stick is used in combination with a laser beam system to measure the difference between the actual elevation and the desired elevation at any given location.
Earth moving equipment is used to move soil and excavate for civil engineering projects. An underground pipe laid in a ditch to carry liquids conveyed by gravity must have a uniform and constant change in elevation. If the pipe has portions that are lower than planned and portions that are higher than planned, liquid will be held in the low spots and solids will settle out of the liquid in these low areas. Over a period of time, the capacity of the pipe will be decreased and the pipe may even become plugged.
A building foundation must be level or at least have level sections and steps with a known elevation change. If the foundation is not level, building walls are unlikely to be vertical. Building walls that are not vertical are generally weaker than planned and could overtime collapse.
Roads and airport runways are generally not level. However they must have sections with a uniform change in elevation. They may also have side slopes in a direction transverse to the direction of vehicle traffic to carry water away. High areas and low areas can hold water and force vehicles to reduce speed. High spots in low areas on a runway can render a runway unusable for high speed aircraft. Such areas can also increase loads on aircraft structures and reduce the useful life of aircraft.
The above examples relate to structures that require careful measurement of elevation during construction. Many more examples could be given.
Civil engineers and others have used a transit and a measuring stick to measure and calculate elevations at selected positions. These devices have required skilled individuals and meticulous records to avoid mistakes in measuring and in calculating results.
Lasers are available today to assist in determining elevations. Such devices can improve the accuracy and speed up the measuring process. However, the measuring stick generally has a graduated scale that starts at the surface and extends upward. When using a laser and a measuring device, the actual elevation at a given point is measured. Then we determine what the elevation should be. Finally the deviation from the desired elevation is calculated. Once the deviation is known, the information is given to a machine operator and he can make required changes. These changes are usually made by removing or adding materials such as rock and soil.
The measuring procedure takes time. While measurements are taken, calculations are made and the results are relayed to a machine operator, the operator and an expensive earth moving machine are frequently idle. This idle time can be very expensive.
Mistakes are frequently made when calculating the results of a elevation measurement. In some cases one measurement is subtracted from another measurement or calculation. In other cases a measurement is added to another measurement or calculation. It is easy to add when you should have subtracted it is also easy to make errors when adding or subtracting measurements that are to the nearest sixteenth of an inch. Making such calculations is, as mentioned above, time consuming.
The civil engineering elevation measuring stick is for use in a laser beam measuring system. The measuring stick includes a primary pole with a top end and a bottom end. A secondary tube telescopically receives the primary pole. The length of the secondary tube from the secondary tube top end to the secondary tube bottom end does not substantially exceed half the length of the primary pole. Four flat secondary walls of the secondary tube extend from the secondary tube bottom end to the secondary tube top end. A pair of spaced apart bottom apertures adjacent to the secondary tube bottom end pass through each of the four flat secondary walls. A pair of spaced apart top apertures adjacent to the secondary tube top end pass through each of the four flat secondary walls. A top ball bearing is positioned in each aperture of the pairs of spaced apart top apertures. A bottom ball bearing is positioned in each aperture of the pairs of bottom ball bearing apertures. Ball bearing retainers hold the top and bottom ball bearings in the apertures. The top and bottom ball bearings prevent contact between inside surfaces of the secondary tube and the primary pole thereby allowing the secondary tube to move freely on the ball bearings between the primary pole top end and the primary pole bottom end. A top end cap and a bottom end cap on the primary pole limit movement of the secondary tube relative to the primary pole. Laser beam receiver mounting surfaces are provided on the secondary tube. At least one measurement scale is provided on the primary pole to measure the distance the secondary tube is moved relative to the primary pole from an index position when a laser beam receiver clamped to the secondary tube is centered on a laser beam. The measured distance indicates the distance a surface supporting the bottom end of the primary pole is above or below the desired elevation thereby indicating how much material is to be removed or how much material is to be added.
One version of the measuring stick includes a spring that urges the secondary tube toward the primary pole top end. With this version, the index point from which measurements are taken is at the top of the primary pole. This version is used when excavating and accurately indicates how much material remains to be removed.
The other version of the measuring stick has an index point, from which measurements are taken, in the center portion of the primary pole. Two scales are provided on the primary pole. Both scales start at the index point. The upper scale increases as you move up from the index point. The lower scale increases as you move down from the index point. A viewing aperture with a position indicator is provided in a wall of the secondary tube. The upper scale encase the quantity of fill that is required. The lower scale indicates the quantity of material that is to be removed. With this version, a clamp is provided to hold the secondary tube in a fixed position relative to the primary pole while the scales are read.
Both versions of the measuring stick measure the deviation from the desired elevation without the need to make calculations. Eliminating calculations in the field saves time and reduces errors.